The present invention relates generally to the treatment of neurological injury and dysfunction associated with central nervous system trauma. In particular, the invention is directed to the identification of proteins which induce neuronal regeneration.
The peripheral nervous system (PNS) comprises highly organized groups of axon fibers or nerves external to the brain and spinal cord, such as the nerves in the limbs. In response to nerve damage, the peripheral nervous system often attempts to repair itself. While the return of lost functions is usually incomplete, generally the injured organism can adapt and function.
By contrast, damage to the central nervous system (CNS), comprising the brain and spinal cord, is generally more serious, usually causing permanent severe disability or even death.
A number of conditions are known to affect both growth and spontaneous regeneration in nerves, but the underlying mechanisms are not well understood (Gibson et at, In Compend. Contin. Educ. Pract. Vet., vol. 11, pp., 1989, 938-945; and Daniloff et al., J. Cell Bio., 1986, 103:929-945). These conditions include the location of injury, the type of injury, the severity of injury, and the age and general health of the patient.
It has been reported that minor prior recoveries somehow prime the nerve for greater recovery in secondary lesions, for example, recovery from an earlier compression injury.
There are no previous reports of an effective treatment for injuries to neurons of the central nervous system, i.e., the brain and spinal cord (see, M. Walker, New Engl. J. Med., 1991, 324:1885-1887.
The lack of effective treatments for nervous system injuries may be due to an insufficient understanding both of the formation of the nervous system and of its responses to injuries. Several attempts have been made to electrically stimulate injured nerves to try to cause regrowth; recovery was highly variable and inadequate (see, B. Sisken et al., Restorative Neurology and Neuroscience, 1990, 1:303-309; see generally J. Daniloff et al., xe2x80x9cThe Molecular Bases of Nerve Regeneration,xe2x80x9d in S. Malhotra (ed.), Advances in Neural Science, vol. 2, 1993). The method that is currently used most often to close gaps in severed nerves uses grafts of the patient""s own sensory nerves, typically taken from the ankle; a minimal degree of recovery and permanent analgesia of the donor foot are the usual results.
Because an injured spinal cord has very limited ability to recover spontaneously, and because the consequnces of spinal cord injuries can be so serious, there is a particular need for an effective treatment of spinal cord injuries. Paralytic spinal cord injuries in the United States alone occur at the rate of about 10,000 per year. Although the mortality rate is less than 10%, approximately 720 Americans per million population are permanently disabled as a result of spinal cord injuries. Most of the injured are young people in the most productive stage of life.
Following injury to neuronal cells in the central nervous system, there is often an abortive attempt by injured neural cells to generate new cellular extensions (dendrites and axons) in order to reestablish inter-neural contacts. In the central nervous system, these nerve sprouting and regeneration activities are often modest and only poorly sustained such that regeneration following stroke, trauma, spinal cord injury, etc., does not usually occur.
Thus, there is a need in the art for material and methods for treating neuronal injury.
The present invention addresses this need. Applicants have surprisingly discovered that a neuron-specific armadillo proteinxe2x80x94Neural Plakophilin Related Armadillo Protein (NPRAP)xe2x80x94causes the development of numerous long, cellular extensions, which are similar to axonal sprouting observed during neuronal regeneration and synapse formation.
One aspect of the invention is directed to a method of stimulating growth of nerve cells, which method comprises contacting the nerve cells with an hNPRAP having nerve growth stimulating activity in an amount effective to cause nerve cell growth.
In a specific embodiment related to a method of stimulating growth of nerve cells, the method comprises contacting nerve cells with an hNPRAP stimulating agent in an amount sufficient to induce the expression of an hNPRAP and cause nerve cell growth.
A further related aspect of the invention is directed to a method of stimulating neuronal regeneration in a mammal, which method comprises administering to the mammal in need thereof an effective amount of an hNPRAP or an effective amount of an hNPRAP expression stimulating agent as set forth above.
A further aspect of the invention is related to a pharmaceutical composition comprising an hNPRAP having nerve growth stimulating activity, and a pharmaceutically acceptable carrier.
Yet another aspect of the invention is related to a pharmaceutical composition comprising an hNPRAP expression stimulating agent and a pharmaceutically acceptable carrier.
In a specific embodiment, the invention provides a pharmaceutical composition comprising an hNPRAP gene therapy vector, which vector comprises a polynucleotid encoding hNPRAP and a promoter for expressing hNPRAP, and a carrier. Naturally, such gene therapy vectors are also part of the invention as well.
A further aspect of the invention relates to a method for identifying substances that modulate the expression of hNPRAP, which method comprises contacting cultured cells that express hNPRAP with a test substance measuring levels of hNPRAP, as compared to a control in which the same cells that express hNPRAP are not contacted with the test substance, as an indication of modulatory activity of said test substance.
These and other aspects of the invention are disclosed more fully in the accompanying detailed description.